Artificial denture

ABSTRACT

COMPLEMENTARY UPPER AND LOWER ARTIFICIAL DENTURES, EACH WITH A DEVELOPED BASE CARRYING BLOCKS OF ARTIFICIAL POSTERIOR TEETH, THE UPPER AND LOWER POSTERIOR TEETH OF SAID DENTURES HAVING MEETING OCCLUSAL SURFACES WHICH ARE CENTRALIZED ANTERO-POSTERIOLY AND DIVIDED INTO LINGUAL AND BUCCAL PARTS, THE LINGUAL OCCLUSAL PART OF SAID UPPER TEETH BEING NORMALLY HORIZONTAL AND RELATIVELY WIDE WITH THE BUCCAL PART RELATIVELY NARROW AND SLOPING A FEW DEGREES UPWARD AND OUTWARD, WHILE THE LINGUAL OCCLUSAL PARTS OF SAID LOWER TEETH ARE ALSO NORMALLY HORIZONTAL, RELATIVELY NARROW AND THE ONLY CONTACTING AREA, THE OCCLUSAL BUCCAL PART SLOPING A FEW CALIBRATED DEGREES DOWNWARD AND OUTWARD AND AWAY FROM THE ESSENTIALLY HORIZONTAL UPPER TEETH FORMS, SO THAT SWALLOWING CONTACT AND CHEWING TRANS-BOLUS PRESSURES ARE EXERTED DOWNWARD AND INWARD ON THE USUALLY LESS STABLE LOWER DENTURE, EFFECTING A STABILIZING ACTION THEREON WITHOUT LESSENING THE STABILITY ACTION DENTURE, SAID DENTURE TEETH APPROXIMATING THE WIDTH OF THE NEUTRAL TEETH AND BEING ARMORED BY HARD WEAR-RESISTANT METAL ALLOY, OR PROCELAIN-FACED METAL ALLOY, CHEWING SURFACES WITH CUTTING BLADES RUNNING TRANSVERSELY ON THE OCCLUSAL CHEWING SURFACES AND HAVING MUSCLE-MOLDED BUCCAL BASES WITH SIDES EXTENDED AS BULGES TO AVOID FOOD ENTRAPMENT.

1971 c. M. MOORE ARTIFICIAL DENTURH Filed May 21, 1970 FIG. 1

m E R 0 mo vM M S E L R A H C ATTORNEY NOV. 30, 1971 c MOORE 3,623,225

ARTIFIC IAL DENTURE Filed May 21, 1970 3 Shccts.3hoot 2 IN V: 0R. CHARLES M. MOORE IiY ATTORNEY NOV. 30, 1971 c MOORE ARTIFICIAL DENTURE 3 Sheets-Sheet 5 OOON mumou 89 OOO OOON

Filed May 21, 1970 BITING FORCE, F, GRAMS INVENTOR. CHARLES MOORE ATTORNEY United States Patent 3,623,225 ARTIFICIAL DENTURE Charles M. Moore, 205 Park St., Montclair, NJ. 07042 Filed May 21, 1970, Ser. No. 39,358 Int. Cl. A61c 13/00 U.S. Cl. 32-8 22 Claims ABSTRACT OF THE DISCLOSURE Complementary upper and lower artificial dentures, each with a developed base carrying blocks of artificial posterior teeth, the upper and lower posterior teeth of said dentures having meeting occlusal surfaces which are centralized antero-posteriorly and divided into lingual and buccal parts, the lingual occlusal part of said upper teeth being normally horizontal and relatively wide with the buccal part relatively narrow and sloping a few degrees upward and outward, while the lingual occlusal part of said lower teeth are also normally horizontal, relatively narrow and the only contacting area, the occlusal buccal part sloping a few calibrated degrees downward and outward and away from the essentially horizontal upper teeth forms, so that swallowing contact and chewing trans-bolus pressures are exerted downward and inward on the usually less stable lower denture, eifecting a stabilizing action thereon without lessening the stability of the opposing denture, said denture teeth approximating the width of the natural teeth and being armored by hard wear-resistant metal alloy, or porcelain-faced metal alloy, chewing surfaces with cutting blades running transversely on the occlusal chewing surfaces and having muscle-molded buccal bases with sides extended as bulges to avoid food entrapment.

SETTING AND OBJECTS OF THE INVENTION This invention is concerned with improvements in artificial-human dentures, particularly with the posterior artificial denture teeth.

The invention provides for maximal artificial denture stability force and pressure distribution in function as well as parafunction. It effects increased masticating efficiency with minimal force application, maximal comfort and permits optimal esthetics in that it permits the anterior artificial teeth to be placed where the natural teethwere. It further provides equitable pressure-distribution on the natural ridge foundations in the function of normal salivary de'glutitory bracing.

The invention further lessens any damage such as soreness, bruising or accelerated resorption of the patients artificial denture foundation ridges in the functional acts of mastication and the numerous bracing contacts in the swallowing of saliva, as well as any nonfunctional acts of clenching, sliding, or doodling with the artificial dentures. It also ofiers a structural allowance for artificial denture settling and normal foundation ridge resorption by eliminating or minimizing the unfavorable inclined plane and lever action of conventional artificial dentures which cause rocking, shunting, tilting or shifting.

The opposing occlusal areas of the substitute posterior tooth forms of this invention consist of a dual pitch based on the laws of the inclined plane and the lever, and calibrated from a research project with measurements and computations of over two hundred edentulous casts.

The artificial denture bases should cover as large a hearing area as possible without impingement on the muscle attachments to the jaw bones, which would tend to move the artificial dentures and/ or injure these tissues. This maximal area coverage distributes the functional forces to more of the natural base areas, thus lessening the pressure per unit area.

The artificial denture bases bearing or seating areas also should be exact negatives of undeformed, healthy ridge foundation tissues captured at rest.

The facial and lingual surfaces of the denture bases should be fully formed functionally. This is done by adding a wax or equivalent impression medium which flows at 98.6 F. or mouth temperature to these surfaces on preliminary undersized resin denture trays which include a simulation of the proposed occlusal scheme. With these in the mouth, the patient is required to simulate all possible movements of the facial and masticatory muscles, thus molding the wax and forming by the interaction of the facial and masticatory muscles and tongue, the dynamic contours of these surfaces. These molded surfaces are preserved by later transformation into a hard plastic material.

THE PROBLEM In complete artificial dentures and large artificial removable partial dentures, a unique problem is presented, viz, a problem in stabilization or retention of the artificial dentures due to the substitution of a relatively flat denture base, usually of resin composition, holding artificial substitute tooth crown forms, as compared to natural roots encased in the jaw bones holding the natural tooth crowns.

The complete upper and complete lower artificial dentures differ in their basic means of retention or stabilization. The maxillary or upper denture covers approximately one third more base area, in that said area includes the palate. The hard palate is considered one of the least changing of anatomic structures.

The upper or maxillary complete artificial denture almost invariably effects a seal at its peripheries by being embedded in the muco-buccal fold soft tissues and by a raising of the posterior denture border thus embedding this back periphery into a small portion of the soft palate tissues. In this way, when air is completely expelled from underneath the denture, atmospheric pressure is enlisted to retain the upper denture by suction until a dislodging force breaks the seal. The utilization of this retention phenomenon plus a larger base gives the complete upper artificial denture a definite retention or stabilization advantage in almost all cases over the mandibular or lower complete denture.

Both upper and lower dentures, when well-fitting, are aided in retention and stabilization to a small degree by interfacial surface tension, viz, an even, thin layer of saliva between the denture and mucosa surfaces, utilizing to some degree the physical phenomena of cohesion and adhesion.

The mandibular or lower complete artificial denture, in addition to its smaller base-bearing surface cannot be sealed in the same way as the upper denture. It further is more readily upset by the very mobile tongue, the muscle attachments of which tend to push against its inner borders. It is also a replacement on the movable jaw member, the upper jaw being finmly afifixed by nature to the skull. Thus, it can readily be seen that there is a marked difference in retention and stabilization potential. This invention tends to overcome this imbalance of retention and stabilization potential.

The denture base, which is the holding mechanism for the artificial crown forms, rests on ridges of a remaining specialized bone which formerly retained the roots of the natural tooth crowns. All of this specialized bone does not disappear after tooth extractions and has been shown clinically to be maintained by the equitably distributed pressure stimulation from stable artificial dentures while it tends to be more readily resorbed under rocking or unstable artificial dentures. Excessive extraneous movement of the dentures, such as rocking, tetering, and

shunting, has a cumulative effect in accelerating bone resorption by a gradual increase in length and magnitude of the blows to the supporting tissues until in many cases, all alveolar bone ridges are gone, often including part of the basal or skeletal bone.

These foundation ridges are covered by a membranoustype tissue of varying thickness and resilience called the mucoperiosteurn which is bathed in saliva and a mucin secretion, a solution of varying viscosity. Thus this situation at best ofiers a slippery and relatively ineffective holding or stabilizing foundation for the denture bases holding the tooth crown substitutes, as compared to natures method of supporting and preventing excessive or extraneous movement of the natural tooth crowns by a root system, viz, individual roots encased in the relatively hard bone tissue of the jaws.

In short, artificial denture base support is on bone, with the intervening slippery and slightly resilient mucoperiosteum; while the natural denture is in bone, with an intervening relatively non-resilient and thin root covering called the periodontal ligament or membrane. It is obvious then that there is a very wide gap between attachment values of artificial and natural dentures. The complete artificial denture (substituting for loss of all teeth) and the large removable artificial partial denture (usually substituting for the loss of posterior teeth) present a real problem in retention or stabilization. This lack of firm bracing of the artificial dentures in chewing further decreases their efficiency in function.

Thus, it is seen that the complete artificial denture, in effect, has but one large relatively ineffective root or foundation; the denture base covering the ridges; while normal natural teeth each have from one to three roots per tooth crown, the lengths of which approximate two or more times the crown height fixed and encased in hard bone. In other words, one complete artificial denture tooth crown out of alignment will cause deleterious defiective movement of all other tooth crown substitutes with their common base, while this is not true of the individually fixed natural teeth.

An object of the invention is the provision of artificial back teeth wherein the lingual occlusal part of the upper teeth are normally horizontal and relatively wide, while the lingual occlusal part of the lower teeth are also normally horizontal and parallel to the upper horizontal areas but relatively narrow, the occlusal buccal parts sloping downward and outward and away from the upper horizontal occlusal platform, thus forming a dual pitch. This effects a stabilizing action particularly on the lower block of teeth by utilizing two basic physical laws, namely: the law of the inclined plane and the law of the lever.

Another object of this invention is to improve the cutting and chewing efficiency of the occlusal surface of the teeth of artificial dentures by providing transverse cutting blades on the mandibular occlusal surfaces which offer guillotine-type food cutting efliciency. This increased chewing efiiciency lessens the needed pressures on the sensitive natural ridge foundations.

A further object of this invention is to provide armored cusps on the occlusal surfaces of the posterior teeth; the armored occlusal surfaces reducing to a minimum the dulling of the cutting blades, the wearing away and breakdown of the occlusal surfaces of the teeth and preventing loss of vertical dimension while also preventing the chipping of the teeth.

Still further objects of the present invention reside in the details of construction of the individual teeth and in the construction and relationship of the occlusal surfaces of the upper and lower posterior teeth which insures their greatest biting and masticating efficiency and the least possible likelihood of cuspal interference in lateral or sliding movements or displacement of the plates from proper position within the mouth and prevents an imposition of deleterios strain on the mucous tissues or imposition of direction upon the mandibular motion.

These and ancillary objects of instructural features of merit are attained by this invention, a preferred embodiment of which is set forth in the following description and illustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an occlusal surface view of the respective upper and lower artificial dentures, including denture teeth constructed in accordance with my invention.

FIG. 2 is a fragmentary laterally-diagonal view of the right hand portion of the mandibular artificial denture of FIG. 1.

FIG. 3 is a vertical cross-sectional view of the lower denture, on the line III-III of FIG. 1 in the direction of the arrows, with the upper denture properly positioned above the lower denture and a bolus of food in place.

FIG. 4 is a fragmentary view corresponding to the left hand part of FIG. 3, but showing the increase in tilting and/or shifting when imitation cusp inclined planes are used on artificial denture crowns in an attempt to imitate the natural crown form.

FIG. 5 is an enlarged sectional view of a fragmentary portion of the left side of FIG. 3 showing the relation of the dual pitch occlusal surfaces and the lingual contact area location.

FIG. 6 is an elevational view of the assembled dentures of FIG. 3 showing the right hand side of said dentures and the extent and location of the sole contact and chewing areas centralized from front to back.

FIG. 7 is a diagrammatic cross section through a human head in approximately the center of the centralized tooth forms and artificial dentures embodying my invention, with the tooth forms in occlusal contact, viz, the mandibular lingual bracing platforms in contact with the maxillary parallel occlusal tables of the artificial denture substitute tooth forms and showing the muscle-molded denture contours offering muscle handles to utilize the tongue-circumoral muscle synergy for additional stability.

FIG. 8 is a chart, including a cross-sectional diagram of artificial denture teeth, for showing the variation in the lower denture stabilizing cross arch seating of transbolus forces in the angle the lower buccal occlusal surface makes with the horizontal, the tilting of cross-arch unseating force caused by presented inclined planes of conventional tooth forms, and that a minimal transverse, downward and outward pitch on the lower tooth forms of approximately three to five degrees can be utilized to effect cross-arch seating and thus maintain the approximate width of the previous natural tooth crowns.

DETAILED DESCRIPTION Referring to the drawings in detail, there is shown in FIGS. 1, 2, 3, 5, 6 and 7, an upper artificial denture 11 and a lower artificial denture 12. The denture 11 comprises a desirably resin-type base 13 in which are embedded upper teeth 14 while the mandibular or lower denture 12 comprises a desirably resin-type base 15 in which are embedded lower teeth 16. The desirably onepiece occlusal segment 17 on each side of the lower denture is composed of a narrow lingual salivary deglutitory bracing contact portion 18 which leads in food bolus penetration, thereby approaching knife efliciency. It is the only part which engages during contacting closure. The reverse pitch occlusal contact portion 19 is provided with transverse cuttingblades 21 to effect multiple guillotine-type cutting action on a food bolus, with a lessening of necessary chewing pressures. In between the cutting blades are grooves open on the buccal aspects to avoid food impaction. The pitch or inclination of the portions 19 and 21 is downward from the tongue side toward the buccal side, desirably about four degrees from the horizontal.

The tooth crown body 22 is desirably of approximate natural tooth color and contour. It is usually made of a resm-type material giving a slight resilience or cushioning, while the occlusal surface is usually composed of a hard wear-resistant material. Examples of some metal alloys which I contemplate for such use are chromiumcobalt, gold and thin porcelain veneering fused to gold or chromium-cobalt alloys. This tooth crown body forms lessens in height from the front to back where it is less readily seen, if at all. The anterior artificial tooth crowns 23 are shown and are not in occlusal contact in centric, posterior or power closure.

FIG. 3 diagrammatically represents a cross section of complete upper and lower artificial dentures in approximately the centralized first molar area, while utilizing the posterior occlusal forms of this invention. The relatively stable upper artificial denture base 13 is shown with developed facial or cheek surfaces 24 adapted to functionally fill the natural buccal pouches on both sides. The body of the artificial crown portion is composed of a very slightly resilient resin-type tooth-color material.

The occlusal parts 25 of the upper tooth forms are desirably made of a hard wear-resistant metal alloy with bodies like the parts [17 of the lower denture. The occlusal surface of each part is composed of a relatively-wide generally horizontal area 26 which is approximately perpendicular to the line of closure and an upwardly-angled relatively narrow area 27. The posterior form generally used in the mandibular or lower complete denture is represented here by the resin-type body 28, the narrow lingual contact area 29 (salivary deglutitory bracing platform) and the reverse pitch area 31 with the transverse cutting blades.

The fully developed complete mandibular denture base 15 is shown with a buccal or cheek side convexity which tends to prevent cheek-biting and offers favorable inclined plane muscle handle stabilization and the lingual or tongue side concave surface to accommodate and utilize the tongue in effecting stabilization. The angle of the reverse pitch 32 and the angle 33 of the narrow upward pitch on the maxillary form are depicted.

The resistant food bolus 34 gives rise to inclined plane and lever action on the running fulcrum of the natural ridge 35 and a turning moment 36 with forces, 37 carried across the arch via the rigid denture base, resulting in a downward or seating force 38 on this side of the arch. It must be noted that were the angle 32 reversed, as in most conventional artificial dentures, the force on the opposite side of the mandibular denture would be a lifting, tilting or unseating force.

FIG. 4 shows the increase in tilting and/ or shifting when the conventional imitation cusp inclined planes are used in artificial denture crowns, in an attempt to imitate the natural crown form, and increase in levers arms a, b and c, as natural ridge resorption takes place. Even with the cuspal or articular occlusal inclined planes lessended, this force translated through the resistant food bolus 34 would not eliminate this unfavorable physical phenomenon. The approximate direction of masticating closure is shown by upward arrow 39; the resultant transbolus unstabilizing force, by downward and outward arrow, 41, (the left side is the buccal or cheek side and the right side of the drawing is the tongue or lingual side). Tooth crown 42 is on the upper which is almost invariably the considerably more stable denture. The lower conventional anatomic tooth crown 43; the denture base with flanges, 44, and the natural ridge base, 45, are shown.

FIG. 2 in its forward position shows a perspective view of the posterior occlusal form usually used in he mandibular complete artificial denture. Left and right forms are shown in FIG. 1 (lower drawing) as seen from above and facing front. The reverse pitch area with transverse cutting blades 21 and 46 and rounded iii-between depressions or valleys open on the buccal side to avoid foood packing. The narrow horizontal deglutitory bracing platform and only occlusal contact area of this form is shown at 29. The bulge of the simulated resin-type tooth crown body is designated 47. When used in the mandibular denture, the drawing presenting the form on the left side is used on the right side of the denture and the form represented on the right side is used on the left side of the denture. When these forms are used in the maxillary or upper artificial denture, the left and right forms are reversed.

FIG. 1 also illustrates in upper plan the maxillary or upper posterior substitute tooth form which is used on a complete upper or large removable partial denture to oppose the mandibular tooth forms. The occlusal surfaces are essentially monoplane and horizontal which is the same as area 26 in FIG. 5 and a narrow upwardly inclined area which is the same as area 27 in said figure. Occlusal area 26 has curved ridges and area 27 has straight transverse ridges as shown. These surface areas are centralized, as shown by reference to the small central circle for each denture, and usually armored by hard wear-resistant gold or chromium-cobalt alloy, or equivalent wear-resistant material, or metal alloy veneered with fused and bonded tooth color porcelain.

Centralization of the closure contact and chewing areas from front to back effects optimal stabilization of the artificial dentures for the following reasons:

(1) The artificial denture is not in any way fixed in bone as are the natural teeth by roots which are encased in bone, but rests on a relatively flat, somewhat slippery and resilient mucoperiosteum base. The anterior or front artificial teeth when properly placed in the position of the extracted natural counterparts are almost invariably anterior to the natural anterior ridge; with any contact thereon causing unseating and a tilting lever action, with the anterior ridge acting as a fulcrum. (Patients learn to incise by pushing upward and backward on the upper denture.) Contacting artificial teeth at the back or posterior portion of the mandibular denture would place a downward force on an inclined plane represented by the beginning of the ascending mandibular, rami (upward curve of lower jaw) thus tending to unseat by shunting the denture in a forward direction.

(2) The anterior ridge has been shown to be unsuited clinically for contact pressures since numerous cases present with considerably abused tissues in this area where this contact was permitted or developed. Epuli fissurata, bruised and inflamed tissue requiring surgical excision are common in these cases. This is somewhat supported by the fact that nature places the larger two and three-rooted molar natural teeth in a centralized position from front-to-back while placing the smaller onerooted incisors and cuspids anteriorly as well as the smaller second and third molars posterior to these areas.

-.(3) It has also been demonstrated by miniature radio transmitters placed in tooth restorations in natural and artificial tooth crowns that the second bicuspid first molar centralized areas are the predominant areas used for mastication.

(4) An approximation of the parallelogram of mandibular closure muscle force shows these centralized areas to be mechanically favorable by adherence to the basic mechanical tenet of base plane perpendicular to force for maximal stability.

(5) The occlusal contact areas approximate the second biscuspid and first molar locations of the former natural teeth or a slightly longer antero-posterior dimension, the area of which is centralized antero-posteriorly (front to back). These are the approximate areas in which the artificial posterior tooth forms of this invention are placed. The occlusal surfaces of these forms are also placed so that they are perpendicular antero-posteriorly to the essentially vertical resultant closure forces of the jaws, and as parallel as possible to the mean planes of the edentulous foundation ridges. This places the masticatory areas in their natural and most favorable positions relative to closure muscle force resultants and proven natural chewing areas.

(6) It further stabilizes the arrangement by satisfying the basic mechanical principle of force application perpendicular to base plane. In cases of unfavorable jaw relation, i.e., lack of parallelism of the mean centralized natural ridge base areas, comprises are made by closer parallelism to the least favorable arch, viz, the jaw arch that offers the least stabilization potential which is usually the mandible. The fact that the closure contact substitute tooth forms of this invention are relatively short anteroposteriorly, facilitates this compromise, i.e., lessens any inclined plane length necessitated by a presented jaw divergence.

(7) The fact that the occlusal contacting and chewing areas are relatively short antero-posteriorly and furnish the sole contacting areas, practically eliminates tilting or shunting inclined plane action as settling and resorption of the natural ridge foundation take place, as compared to the tilting and shunting of full arch or nearly full arch contact with cuspal and/or articular inclined planes of conventional tooth forms. In this regard, the tooth forms of this invention are, in effect, somewhat self-adjusting.

The ridges in the horizontal occlusal area 26 in FIG. are curved so as not to trip in any way with contacting area 29 and further to aid comminution of the food bolus. The ridges in occlusal area 27 are transverse and open buccally and lingually to act as sluice ways and avoid food entrapment. The body of the crown forms, 17, are of tooth color resin-type material. The complete chewing cycle 40 (in FIG. 3), as observed from the front, with patient chewing on the right side, is teardrop in shape and essentially vertical near contact or in the approximate bolus area, although it is sometimes noted as upward and slightly inward, empty closure or the bracing contact for swallowing saliva is an essentially vertical closure.

FIG. 5 is an enlargement of the upper (maxillary) and lower (mandibular) cross section of opposing tooth forms as shown on left side of drawing, FIG. 3, but without bolus and in bracing contact. This cros section represents the approximate center of the embloc tooth forms. In addition to the areas heretofore mentioned are the retention beads and/or retention loops 51 maintaining a mechanical bond for the usually-used metallic occlusal surface portions. The base development convex buccal surfaces 49 are illustrated in part, giving rise to stabilizing inclined plane action as illustrated in FIG. 7, as well as permitting the use and most facorable positional setting of the tooth forms without the possibility of cheek-biting. It will be mother that on contact closure the only contacts are in the deglutitory bracing platform 29 and the upper horizontal and parallel occlusal table 26 of the opposed complete artificial dentures (or natural teeth).

The occlusal contact areas approximate the second bicuspid and first molar locations of the former natural teeth or a slightly longer antero-posterior dimension, the area of which is centralized antero-posteriorly (front to back). These are the approximate areas in which the artificial posterior tooth forms of this invention are placed. The occlusal surfaces of these forms are also placed so that they are perpendicular antero-posteriorly to the essentially vertical resultant closure forces of the jaws, and as parallel as possible to the mean planes of the edentulous foundation ridges. This places the masticatory areas in their natural and most favorable positions relative to closure muscle force resultants and proven natural chewing areas.

It further stabilizes the arrangement by satisfying the basic mechanical principle of force application perpendicular to base plane. In cases of unfavorable jaw relations, i.e., lack of parallelism of the mean centralized natural ridge base areas, compromises are made by closer parallelism to the least favorable arch, viz., the jaw arch that offers the least stabilization potential, which is usually the mandible. The fact that the closure contact substitute tooth forms of this invention are relatively short anteroposteriorly, facilitates this comprise, i.e., lessens any inclined plane length necessitated by a presented jaw divergence.

In this invention the occlusal contact areas are, in effect, centralized transversely (medio-laterally or side-to-side) in unilateral chewing without encroachment on the tongue space by the incorporation in the occlusal surface design of the artificial tooth form substitutes of a calibrated reverse pitch (slant downward and outward toward the cheeks as seen from the front), in addition to the narrow horizontal contacting occlusal portion. The narrow horizontal inner portion comprises about one quarter or less of the width of the occlusal surface (lingual aspect), While the reverse pitch outer area comprises about three quarters or more of the occlusal surface. The narrow inner surface horizontal area (deglutitory bracing plane) is the first and only occlusal contact in jaw closure and acts as a bracing contact in normal salivary deglutitory bracing, and acts as a clearance plane in that it permits sliding contact (protrusion and/ or lateral) without introducing inclined planes.

With conventional occlusal forms such as natural cusp imitation or slight modifications thereof, or with the usual buccal or cheek side of mandibular occlusal surface form higher than the lingual surface form area (slant downward from cheek side to tongue side, curve of Wilson) or monoplane (flat) occlusal surface forms set to a transverse curve with a concavity facing upward or with an angled tilt of the mandible in the chewing stroke, angle a becomes minus and the opposite ridge downward seating forces 37 are received and become upward (lifting) or tilting forces tending to unseat (tilt or rock) the artificial denture.

In the use of this invention, the degree of the reverse pitch portion of the surface of the occlusal contact form is kept to a minimum, so that overall occlusal surface food table and crown body widths approximate the natural teeth occlusal widths, thus aiding the tongue-circumoral muscle synergy in its role of placement and control of the food bolus, speech articulation and comfort. If desired, particu: larly in cases of marked dimensional variance from the average range, closer approximation of the indicated reverse pitch could be computed individually from FIG. 8, with correction curves, although most average size cases will benefit optimally from the usual three to five degree reverse pitch average.

The mandibular eduntulous arch offers the least stable foundation, as compared to the maxillary edentulous arch, with a few exceptions. However, in the partially edentulous state, that is with (anterior and posterior teeth) natural teeth remaining in the mandible, opposing an edentulous upper arch, the stabilization potential of the mandible thus becomes greater than the maxilla (edentulous upper arch). Therefore, the posterior tooth forms usually used on the mandibular denture are used now on the upper denture. This is because these forms direct by inclined plane action transbolus forces towards the center of the foundation. Furthermore, the narrow lingual horizontal contact platform tends to centralize the forces of empty closure con tact including the numerous bracing contacts for the swallowing of saliva. When the lower forms are used thusly, the occlusal surfaces of the natural teeth and/or fixed bridges are contoured by restorations or selective grinding to be in the horizontal plane.

Prior to this invention, when a patient has some or all healthy natural teeth and no natural lower teeth, it has generally been considered necessary to extract all remaining healthy upper teeth and fabricate a complete upper artificial denture opposing the complete lower artificial denture to make the prostheses clinically acceptable. However, with the proper use of the mandibular tooth forms of this invention, alteration by restorations and/or selective grinding of the occlusal surfaces of the presented upper natural teeth to approximate a horizontal plane in the closure contact area, function and comfort can be restored without extraction of the healthy natural upper teeth.

In the prevalent cases in which the patient has only some or all of the mandibular natural anterior teeth, viz, cuspids and/or incisors, it is necessary to construct a large bilateral free-end removable partial lower artificial denture opposing a complete upper artificial denture. Although the stabilization potential of said lower denture is somewhat increased by the clasping of the natural teeth,

the relatively long free-end areas must be given maximal stabilization to avoid torquing with eventual exfoliation of these teeth; therefore the mandibular occlusal forms with maximal base development are used with removable partial denture the same as in the case of a complete lower opposing a complete upper artificial denture. In this way extraneous denture movement is minimized, thus preserving the remaining natural teeth with their biomechanical and psychological contributions.

REVERSE PITCH PLANE CALIBRATION A research study was made with a view to the determination of the minimum angle (in degrees) of reverse pitch needed to produce a positive or seating force on the opposite ridge of the mandibular artificial denture, when unilateral transbolus forces (chewing) are introduced. The ridge crest in the center of the centralized occlusal contact and chewing area of one side to the same area on the opposite side of the arch forms a lever arm, since they are rigidly connected by the solid denture anteriorly. The average ridge crest-to-ridge crest (side-to-side) measurement of over two hundred mandibular artificial stone casts (made from impressions of edentulous patients lower jaw ridges) was 42.46 millimeters.

The ridge crest to occlusal contact surface height forms another lever arm (the ridge crest acting as potential running or elongated fulcrum). These were vertical measurements in the center of the antero-posterior centralized occlusal contact area of the patients mandibular complete artificial denture (corrected where indicated) or constructed mandibular occlusion rims (wax patterns). The occlusal surface height was determined by a line approximating posteriorly the junction of the inferior and middle thirds of the retromolar pads, as determined by accepted average normal natural tooth crown height plane. Anteriorly, the height line was continuous with the accepted height of the incisal surfaces of the lower anterior or front teeth. This latter height was determined by the average lip line-incisor relation of natural teeth aided by a consideration of the degree of bone ridge resorption exhibited. In most cases, the patients artificial dentures were measured or occlusion rims (wax patterns for construction of artificial dentures) with corrections made where necessary. The average ridge crest to occlusal height of the more than two hundred complete artificial mandibular dentures or occlusion rims measured was 12.67 millimeters, as shown by the cross-sectional diagram in the right-hand portion of FIG. 8.

A chart, FIG. 8, was prepared by mathematical computation using these measurements. This chart was com puted on a zero (vertical) chewing angle. The left side line of this figure is calibrated for biting force from zero to eight thousand grams. The bottom line of this figure is calibrated from zero to two thousand grams for denture seating force +F on the opposite mandibular ridge when the reverse pitch is used as in this invention (see cross section diagram of FIG. 8). As shown in the diagram the reverse pitch forms angle +a with the vertical ridge centerline. With normal unilateral chewing, the resistant food bolus will transmit downward (or positive) seating force P In conventional artificial denture occlusions, particularly those with inclined planes formed by natural cusp imitation, the angle a becomes (to the right of vertical centerline) thus reversing the direction of F and forming a lifting force on the opposite side of the arch. Correction curves were graphed to determine the influence of various dimensions of angled chewing stroke, ridge-to-ridge lever arm and ridge crest-to-occlu- F =94.0 grams Having now described my invention in detail in accordance with the requirements of the patent statutes, these skilled in this art will, within the scope of the claims, have no difiiculty in making changes or modifications in the individual parts or their relative assembly in order to meet specific requirements or conditions.

I claim:

1. Complementary upper and lower artificial dentures, each with a muscle-molded fully developed base carrying groups of artificial teeth, the upper and lower posterior teeth of said dentures having meeting occlusal surfaces divided into lingual and buccal parts, the lingual occlusal part of said upper teeth being normally horizontal and relatively wide, with the buccal part relatively narrow and sloping a few degrees upward and outward, while the lingual occlusal part of said lower teeth are also normally horizontal, relatively narrow and the only contacting area; the occlusal buccal part sloping a few degrees downward and outward, so that swallowing contact and chewing trans-bolus pressures are exerted downward and inward on the lower denture, effecting a stabilizing action thereon without lessening the stability of the opposing denture.

2. Complementary upper and lower dentures as recited in claim 1, wherein the cuspal inclined planes, formed by cusps or modified cusps on biting surfaces resembling those of natural teeth and which tend to tilt and shift artificial dentures via inclined plane trans-bolus forces, in particular are omitted.

3. Complementary upper and lower dentures as recited in claim 1, wherein articular inclined planes, such as curves with convexities downward from front to back (or curve of Spee) and side-to-side (or curve of Wilson) as in natural teeth and which tend to tilt and shunt artificial dentures, are omitted.

4. Complementary upper and lower dentures as recited in claim 1, wherein the contacting and chewing area is relatively short antero-posteriorly and centralized from front to back.

5. Complementary upper and lower dentures as recited in claim 1, wherein the only closure contacting surfaces are the narrow lingual horizontal occlusal surfaces of the lower denture and equivalent portions of the relatively wide horizontal surfaces of the upper denture.

6. Complementary upper and lower dentures as recited in claim 1, wherein there is no intermeshing or tripping by occlusal surfaces in lateral excursions or in change of closure contact areas.

7. Complementary upper and lower dentures as recited in claim 1, wherein the narrow lingual horizontal occlusal surface tends to neutralize unfavorable inclined plane and lever action on the dentures.

8. Complementary upper and lower dentures as recited in claim 1, wherein the occlusal buccal parts sloping away from one another produce a positive seating force particularly on the lower denture, tending to equalize the stability potentials of the upper and lower dentures.

9. Complementary upper and lower dentures as recited in claim 1, wherein each group of artificial posterior teeth is formed in one piece.

10. Complementary upper and lower-dentures as recited in claim 1, wherein the sloping surfaces of the lower tooth forms make an angle of about four degrees with the horizontal as determined by computations.

11. Complementary upper and lower dentures as recited in claim 1, wherein the artificial substitute tooth forms simulate the width of the natural teeth, their natural counterparts, thereby presenting a natural occlusal food table width for food bolus placement and control by the tongue-cheek muscle synergy.

12. Complementary upper and lower dentures as recited in claim 1, wherein the'mandibular narrow lingual surface is the leading surface in food bolus penetration, thereby approaching knife efficiency.

13. Complementary upper and lower dentures as recited in claim 1, wherein the buccal crown-bodies and denture base surfaces are fully developed by a musclemolding technic forming bulges which tend to prevent buccal food spillage and entrapment.

'14. A complete lower denture as recited in claim 1, opposing at least some upper natural teeth, made possible by use of the mandibular tooth forms of this invention, with alteration of the natural teeth opposing occlusal surfaces to present a horizontal plane, by at least one of the following operations; restoration and selective grindmg.

15. A complete upper denture as recited in claim 1, opposing at least some lower natural teeth, with mandibular tooth forms of this invention used in said upper denture and the occlusal contacting areas of the lower natural teeth altered to present a horizontal plane, by at least one of the following operations; restoration and selective grinding.

16. Complementary upper and lower dentures as recited in claim 1, wherein a complete upper denture op- 12 poses a lower removable bilateral'free-end partial denture which replaces the mandibular posterior teeth.

17. Complementary upper and lower dentures as recited in claim 1, wherein said teeth are armored by hard Wear-resistant metal alloy occlusal portions.

18. Complementary upper and lower dentures as recited in claim 17, wherein cutting blades run transversely on the occlusal surfaces of said alloy and on the lower effect a multiple guillotine-type cutting action, lessening pressures on the natural ridge foundations.

19. Complementary upper and lower dentures as recited in claim 17, wherein the wear-resistant metal occlusal portions are formed of chromium-cobalt alloy and the tooth crown body portions are of a relatively resilient plastic-type material.

20. Complementary upper and lower dentures as recited in claim 17, wherein the wear-resistant metal occlusal portions are formed of a hard wear-resistant gold alloy and the tooth crown body portions are of a relatively resilient plastic-type material.

21. Complementary upper and lower dentures as recited in claim 17, wherein the wear-resistant metal alloy occlusal portions are veneered or faced with tooth color bonded porcelain or similar wear-resistant tooth color material and the simulated tooth crown bodies are of slightly resilient plastic-type material.

22. Complementary upper and lower dentures as recited in claim 17, wherein the occlusal and crown body portions are made of wear-resistant tooth color plastictype material.

References Cited UNITED STATES PATENTS 1,941,735 l/l934 Berry 32'8 ROBERT PESHOCK, Primary Examiner 

